Currently, the most widely used method of kidney dialysis for treatment of end stage renal disease is hemodialysis. In hemodialysis, the patient's blood is cleansed by passing it through an artificial kidney in an artificial kidney dialysis machine. During dialysis, venous and arterial blood lines convey a patient's blood to and from the artificial kidney. Impurities and toxins are removed from the patient's blood by diffusion across a semipermeable membrane in the artificial kidney. Hemodialysis is generally required three times a week with each dialysis requiring four to five hours in a dialysis center or at home.
Peritoneal dialysis, although used less frequently than hemodialysis, is an accepted method for treating end stage renal disease. It is becoming increasingly a more popular form of dialysis. In peritoneal dialysis, a dialysis solution--also referred to as dialysate--is infused into a patient's peritoneal cavity using tubing and a catheter. The peritoneum, which defines the peritoneal cavity, contains many small blood vessels and capillary beds which act as a natural, semipermeable membrane. This natural membrane may be contrasted with the artificial membrane used in hemodialysis. Nonetheless in both cases, impurities and toxins in the blood are removed by diffusion across a membrane.
In peritoneal dialysis, dialysis solution remains in the patient's peritoneal cavity for a time sufficient for blood impurities to be removed by diffusion across the peritoneal membrane and into the dialysis solution. The impurity-containing or spent dialysis solution then is drained from the peritoneal cavity, typically by means of the infusing catheter and tubing. A fresh supply of dialysis solution replaces the spent, impurity-containing, drained solution.
Dialysis therapy includes two forms of peritoneal dialysis treatment pertinent to the present invention. Continuous Cycling Peritoneal Dialysis (CCPD) uses auxiliary apparatus to cycle dialysis solution through a patient's peritoneal cavity, typically during the sleeping hours. A patient generally undergoes dialysis treatment each night. Intermittent Peritoneal Dialysis (IPD) similarly uses auxiliary apparatus to infuse dialysis solution into the peritoneal cavity and drain dialysis solution from a patient's peritoneal cavity at a rate much faster than in CCPD. Similar to hemodialysis, and unlike CCPD, IPD therapy is conducted intermittently during the week, typically in four to five hour sessions, three times a week. The volumes of dialysis solution are rapidly infused and drained to accomplish the dialysis within this time period. In CCPD and IPD, infusion and draining of dialysate are accomplished using tubing and a surgically implanted, indwelling catheter in communication with the patient's peritoneal cavity.
It would be desirable to provide a safe, automatic apparatus for performing peritoneal dialysis. Such an apparatus would be suitably automatic and convenient so that it can be used by the home patient or by staff in a hospital or clinic. The peritoneal dialysis apparatus would have the capability of performing both CCPD therapy and IPD therapy--in home and hospital environments--with only minor adjustments to the apparatus and without increasing the complexity of a basic apparatus design.
For CCPD, it would be advantageous to provide an apparatus which would selectively infuse different formulations of dialysis solution which are adapted to account for different periods of dwell inside the patient. The last dosage of dialysate administered to CCPD therapy patients dwells in the peritoneal cavity until the next dialysis procedure. This time period could be as long as 16 hours. It would be desirable for the apparatus to infuse a first formulation of dialysis solution during the initial cycles of a dialysis treatment yet having the capability of infusing a second formulation for the last dosage of dialysate administered, that is, a "final fill". The second formulation of dialysate would be chosen especially because of a longer dwell period in the patient.
It would be expedient to provide an apparatus with a stable base. Usually, all but an infusing dosage of dialysate would be stored at a relatively low level. A fixed column, preferably supporting approximately a single infusion dialysate dosage, would be higher than the stored dialysate to provide gravity feed of the infusion dialysate to the patient. Alternatively, the support column would be adjustable to allow control of the head pressure of the infused dialysate.
In some situations, more than a single infusion dialysate dosage would be supported at the support column. For example, in pediatrics, the infusion dialysate in a conventional design container could contain several dosages. Generally, though, total volume of infusion dialysate supported at the column would be less than the volume stored at a relatively low level. This would promote a more stable design.
It would be expedient to reduce the length of the tubing set which carries dialysate from storage to heater to patient and to drain. Apparatus having valves banded together, or ganged, require longer tubing sets since all tubing must be routed to the ganged valves from the isolated stations of the apparatus and back if fluid flow therein is to be regulated by the valves of the apparatus. It would be desirable to provide separated valves which would be appropriately placed for regulating dialysate flow in a tube rather than extending the length of the tube to communicate with the valve.
Tubing set length also can be reduced by using common tube sections for the different dialysate flow paths to and from the separate stations of the apparatus. An apparatus having simultaneous fluid flow between different stations of the apparatus requires duplicate portions of tube sections. It would be advantageous to eliminate this redundancy by providing an apparatus which sequentially controls fluid flow between different stations of the apparatus as opposed to simultaneous flow.
It would be desirable to reduce the complexity and cost of a tubing set by eliminating the need for a specially designed container to hold dialysate for heating and weighing prior to infusion into a patient. An elegant design would be capable of accepting a conventional dialysate container bag at the heater and weigh station thereby eliminating the need for a specially designed container.